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On the science of baguettes, poolish and steam in the oven
Whenever visiting France there is one thing I really really look forward to: visiting a boulangerie, a bakery. The French baguettes are just so good, always fresh (since storing them for even one day will make them go stale) and hard. I also adore the pain au chocolat, a croissant with chocolate filling.
Since we’re not in France that often I decided I had to try making a French baguette myself! Since I didn’t trust any non-French website I decided to google a recipe in French and found one. Why in French? Because I’ve found there are a lot of people calling their white long bread a French baguette whereas it clearly isn’t! Of course, this isn’t the only way to make them, as a French baker will probably be able to tell you.
This French baguette almost tasted like the real thing. It was really crispy on the outside, soft and light on the inside. When making the bread, two special steps seemed to contribute to the result: using a “poolish” & placing a bowl of water in the oven during baking!
Never heard of poolish? Neither did I. A poolish a so-called pre-ferment. It is a mixture of flour, water and yeast that is left to proof and leaven for a few hours before starting the bread making process. In the case of poolish you use an equal weight quantity of water and flour, making it quite liquid.
During this leavening time the yeast ferments. It consumes the sugar in the flour and produces gas (carbon dioxide) as well as flavour. The longer a yeast is allowed to ferment, the more flavour molecules it develops. In a poolish the amount of yeast varies. The more yeast you use, the faster it ferments and the faster the poolish is ‘ready’.
Since the flour is the poolish has had a long time to hydrate it will become noticeably more flexible as well. This is similar to what you see happening when making a no-knead bread. Even though the dough might look stiff at the start,it becomes noticeably more flexible over time. Part of this is due to the hydration of the flour, but it is likely that enzymes in the flour also cause some changes which help strengthen the gluten network.
Difference with a sourdough starter
To make a poolish you need some yeast. Once the poolish is ready to use, that is it has bubbled up, it needs to be used within a few hours. You cannot store a poolish for days on end. (The best way to extend the shelf life somewhat is storing it in the fridge, but this will change the flavour profile.) A sourdough starter on the other hand uses wild yeasts from the air and can be kept alive for months or years on end with the right feeding regime.
Bowl of water in the oven for crispyness
The second trick I used was one I discovered when writing and reading about the history of ovens. I discovered that at the time, when big stone ovens were used, the moisture content in an oven was very different.
These ovens used to be very large and in the first stages of baking bread (or pizza dough) a lot of moisture would evaporate from the dough. This moisture couldn’t really go anywhere, so would just stay in the oven.
Nowadays, ovens aren’t designed for that anymore, so if you have a conventional oven you’ll have to increase the moisture content yourself. I do that be taking an oven proof glass bowl and filling this with boiling hot water which I then place in the oven. Since my oven heats up pretty quickly and water tends to take a long time to heat up, I prefer adding water that’s already pretty hot.
Once the water is hot part of it will evaporate and form steam. Why is this important? I’ve found several sources (one of which is this article from serious eats) which mention the same two main reasons:
- The high moisture content in the oven will keep the outside of the bread flexible for a longer period of time. This should allow it to expand more extensively than without the steam.
- Moisture is good in transferring heat and a high moisture content should increase the temperature transfer at the surface (thus crust) of your bread. Apparently, this should lead to more browning but also a thicker crust.
The reasons make sense to me and my experience with the method has indeed been very positive. Never have I had a bread with such a good crunchy, crispy crust as I had this time!
Good luck and let me know how it went! Also, if you have any other (bread) baking/cooking questions which are related to science, let me know! Who knows you might be featured in a future post.
French baguette recipe
The recipe I used comes from Recette Dessert, I didn’t make a lot of changes since it turned out great the way it did!
Want to read more about poolish? The Weekend Bakery wrote a nice post about its use.
Having used other recipes, this particular one has the right proportions for a small batch of baguettes if you want to experiment. I would suggest using All Trumps flour, or King Arthurs Sir Galahad and doubling the amount if salt. For the technique itself of “folding and kneading” look at John Kirkwoods videos on youtube.
Also, you can experiment with a long poolish ferment in the fridge for a couple of days prior to making bread. Its a fun little project when you’re on lockdown.
Getting the steam right in the oven is tricky. The key is to reduce the volume of air around your dough and concentrate the humidity in that volume. I use the “Mun” method posted on facebook and found it to be the most effective and cost effective. First use a baguette pan to hold the final dough. But you can simply use a thick stone. Put a cookie sheet with 1/2” walls and a stone on the sheet both into the oven during pre-heat. Have a 4” deep alum roasting pan longer than the baguette pan ready. Have one cup of hot/boiling water ready. When it is time to place the dough into oven, place the baguette pan (or simply the dough if you don’t have a pan) on top of the stone. Then cover the dough with the alum roasting pan to create a dome. Then pour the hot water into the baking sheet and it will steam immediately into the alum roasting tray dome. This method produces sufficient humidity and maintains it because you’ve effectively reduced the oversized oven of most home kitchens. The steam is trapped under the dome during the initial bake (15 min). No need to keep spraying or adding more ice cubes, or messing around with lava rocks and damp towels. Try it, you’ll be surprised how effective this is.
when Baking Baguettes do I set the oven to Convection Bake or Just Bake?
You can use both, keep in mind that the convection setting is a little more efficient than the ‘just bake’ setting, so using convection you generally use a slightly lower temperature. Otherwise, both will give you good baguettes (we’ve used both) and I’d recommend testing both to see which works best for your oven (every oven is different!).
Thank you very much! This turned out very, very well for me, and I appreciated both the tips about the poolish and the steam oven. I think I will probably try to increase the salt next time (the bread wasn’t salted enough for my tastes), but the technique and everything else was just perfect. Thanks very much for sharing your tips — much appreciated!!
Glad to hear it worked well for you Julia! And yes, I tend to eat my bread on the less-salty side, you can definitely adjust it to your own personal preferences, we’re all different :-).